Jun 17, 2014 8:04 PM

I recently picked up an interesting a beautiful rock - it instantly caught my eye and is probably the most shiny rock I have ever seen! I found it in the United States (Kansas) and was wondering if anyone would be able to help me identify it. It is fairly heavy and is 12mm by 6.5mm at it's largest point. Thank you to anyone who can help!

Schist is a metamorphic rock - one formed from a different type of rock by high pressure and temperature, which forces the original minerals to recrystallize into new ones in equilibrium with the new physical conditions. We can't really say what the original rock was, but we can identify the minerals that comprise it now. In this case, they include a large percentage of micas, which is why I qualify the name schist with that prefix.

Mica is actually a family of minerals, structurally similar but composed of differing elements. Two common micas are muscovite (light-coloured) and biotite (dark). There's a good chance both of those are present in your specimen. There will be other minerals as well, but I can't ID them from photos; I would need a petrological microscope to look at a thin section of the rock (translucent) under polarized light.

Mica is a phyllosilicate - its structure is like very thin layers of leaves pressed together (phyllon=leaf in Greek). It is that structure that gives mica its reflectiveness.